The present invention relates to a novel antimicrobial compound and a process for producing it. Furthermore, the present invention relates to a novel antimicrobial polymer composite comprising a polymer and the antimicrobial composition.
Inorganic aluminosilicates in which their alkali metal salt component is substituted by microbicidal metals have been known as antimicrobial compositions but antimicrobial compositions of the type contemplated by the present invention that are based on silica gel have not been known. In the conventional antimicrobial compositions based on aluminosilicates, microbicidal metals are uniformly distributed in their whole part including the surface and interior. In view of the structure of those compositions, not a large proportion of the microbicidal metals used is considered to work effectively in actual applications. Such being the case, the microbicidal metals have had to be used in large quantities in order to insure stronger antimicrobial activities. However, if antimicrobial compositions having high contents of microbicidal metals are added to polymers, they are discolored or stained.
It is also known to have a silver compound retained on a silica matrix through physical adsorption by treating the silica with a solution of silver nitrate. A problem with this method is that silver, being not chemically bound to the matrix, is labile and will be readily separated or released from the matrix.
The conventional aluminosilicate based antimicrobial compositions are commercially available in powder form comprising fine particles of 1-20 .mu.m in size. In order to make them convenient for use in aqueous systems, the compositions must be formed into beads, pellets and other shapes that have increased mechanical strength and water resistance. In shaping the powder of conventional aluminosilicate based antimicrobial compositions, a special wet forming method is practiced using binders and other additives and the shaped part is then sintered at elevated temperatures to increase its strength. However, the thus shaped part of antimicrobial aluminosilicates (amorphous) or antimicrobial zeolites (crystalline) are not suitable for prolonged use in aqueous systems because if they are submerged in water, their water resistance deteriorates gradually and in an extreme case they are disintegrated to fines which are no longer effective for the intended purpose.